1. Technical Field of the Invention
The present invention relates to a microstrip array antenna using a dielectric substrate.
2. Related Art
A microstrip array antenna, which comprises a strip conductor formed on a dielectric substrate, has advantages in thinness, low cost of manufacturing, and productivity. Due to these features, microstrip array antennas have been widely used as transmitting and receiving antennas for various radio wave sensors such as a vehicle-mounted radar used in, for example, anticollision systems and adaptive cruise controls (ACC).
One example of the above microstrip array antenna is known in which a plurality of radiation antenna elements are connected with and arranged at a predetermined interval along the two sides of the linearly disposed feeding strip line.
When the microstrip array antenna configured as described above is installed in a vehicle as, for example, an automotive radar, the feeding strip line is commonly disposed so as to be perpendicular to the ground so that the antenna can totally obtain a desired radiation pattern (especially, radiation pattern in the vertical direction). Meanwhile, plane polarization inclined at a predetermined angle (for example, 45° with respect to the ground is preferably used as a radio wave transmitted/received by the microstrip array antenna to prevent interference with a radiated wave from an oncoming vehicle.
Accordingly, a microstrip array antenna is proposed in, for example, Japanese Patent Application Laid-open No. 2001-44752. In this microstrip array antenna, while the whole antenna is disposed in the vertical direction, radiation antenna elements are connected with and arranged along the sides of the feeding strip line so as to incline with respect to the longitudinal direction of the feeding strip line to realize plane polarization inclining with respect to the ground.